Method of producing transformer core laminations from strip stock



1964 A. E. FEINBERG ETAL ,96

METHOD orpaonucms TRANSFORMER CORE LAMINATIONS FROM STRIP s'rocx Original Filed March 19, 1958"; 3 Sheets-Sheet 1 W L'Wozg Oct. 27, 1964 A. E. FEINBERG ETAL 3,153,961

memos 0F PRODUCING TRANSFORMER CORE 4 LAMINATIONS FROM STRIP STOCK Original Filed March 19. 1958 s Sheets-Sheet 2 I 33 I 29.. L K I I i 1964 A. E. FEINBERG ETAL 3,153,961

METHOD OF PRODUCING TRANSFORMER CORE LAMINATIONS FRQM STRIP STOCK Original Filed March 19, 1958 3 Sheets-Sheet 3 1K5 I V A W M MW i W r? m" -1l"l L 1 4: Mi 4 W I. w

; H1 [1H I' 4%; (gzilz United States Patent 0 3,153,961 NETJQD 0F PRGDUCENG TRANSFGPJVECR 0RE LAEZENATIGNS FRGM SIRE lflf Albert E. Feinberg and Julian Neiaitch, Chicago, iii, as-

signors to Advance Transformer -Co., Chicago, ill, a corporation of lllinois Continuation of application Ser. No. 727,017, Mar. 19, 1958. This application June 243, 19-63, Ser. No. 295,359 7 tilaims. (1. 834-3) This invention relates generally to transformer constructions and more particularly is concerned with a novel method of forming the laminations employed in the structure for the core of a transformer, such as for example the type used as part of apparatus for ballasting gaseous discharge devices.

This application is a continuation of our application Serial No. 727,617, filed March 19, 1958, and now abandoned.

Heretofore transformers for use with apparatus for igniting and operating gaseous discharge devices, where formed of the shell type, have been wasteful of the electrical steel sheet metal which is used to form the laminations of the core. The shell type ballast or transformer core of elongate construction which the structure to which the invention is particularly directed compris s a rectangular formation having elongate sides and or g g ends, and a central winding leg mounting the windings upon said winding leg in the spaces formed between the elongate framing sides and the sides of the winding leg. Various shunts and the like were integrally formed either with the winding leg or the outer rectangular shell or both.

In forming such laminations, the shell and central winding leg were punched out of the same blank so that the windows were formed by virtue of removal of the metal between winding leg and shell. Tins metal was thus scrap, and while not exceeding the amount of metal for each lamination, in the manufacture of millions of laminations, the scrap comprised a substantial cost of the ballast, and represented what would otherwise be profit.

It is therefore the principal object of the invention to provide a novel method of forming the core of a transformer which uses laminations formed in a manner substantially to eliminate the scrap sheet metal heretofore produced in the construction of laminations for shell type cores of elongate structure.

It is a further object of the invention to provide such a structure which enables the provision of certain features of construction without the need for complex dies or difiicult assembly procedures.

Still other objects of the invention are to provide a novel method of forming laminations for a transformer core structure which is made up of easily formed laminations having relatively simple configuration and which may be assembled to form a shell type core which includes an elongate central winding leg and windows for windings.

Still another object of the invention is to provide a transformer core construction which will result in a ballast which is efficient and will provide not only a good wave shape but which will also provide a minimum of noise.

With the foregoing and other objects view which will become apparent as a description of the invention proceeds, and which will be particularly pointed out in the claims, the novelty herein lies in the formation of elements of the laminations assembled in a novel manner, and capable of being produced at extremely high spee from strips of electrical sheet steel passing through automatic punch press machine There are illustrated preferred embodiments of the invention and the specific description relates thereto, although only by Way of ill:

tration and to comply with the patent laws, because it will be seen that the invention is capable of wide variation as to minor details.

In the drawings in which the same or similar characters are used throughout the several figures thereof to designate equivalents:

FIG. 1 is a side eleva.ional view, with parts shown in section, of a transformer construction in accordance with the invention and using the new laminations in the achievement of a shell type core, a member used in retaining the transformer in assembled condition being illustrated alongside one end thereof.

FIG. la is a view similar to that of RIG. 1 but of a fragment of the end thereof showing a modified form in which different means are used to retain the laminations and the transformer assemble FIG. lb is a side elevational view of an end clamp for use with the modified form of PEG. la.

FIG. 2 is a circuit diagram of a typical apparatus for igniting and operating two gaseous discharge devices for use with a transformer structure of the invention.

FIG. 3 is a top plan View of a group of lamination elements showing the manner in which the same are nested as punched from a continuous strip, the elements being of formation to be assembled to the structure of FIG. 1 or FIG. la.

PEG. 4 is another top plan view of a group of lamination elements but all being of T formation, and being arranged in nested condition as punched from a continuous strip.

FIG. 5 is still another top plan View of nested laminations showing how the same may be punched from a continuous strip with a minimum of waste or scrap, but all being of L formation.

FIG. 6 is a view similar to that of FIG. 5 but showing a variation in the form of arranging the L formation elements along the continuous metal strip.

FIG. 7 is a diagrammatic view showing the arrangement of lamination elements all of L formation for forming the type of core construction illustrated in FIG. 1.

Generally the invention comprises forming the transformer core of elongate L and T formation elements to make up the shell type core structure or in forming the same of L formation elements alone. In the case of the L and T formation structure, the short legs of two L formation elements abut opposite sides of the elongate leg of a single T formation element and have their long legs arranged parallel with the single elongate leg of the T formation element, and spaced therefrom to form the window or windows for accommodating the windings. The cross arm of the T formation element has its ends abutting the sides of t e long legs of the L formation elements at the ends thereof. The total length of the cross arm of the T formation element is exactly the distance between the inside edges of the elongate legs of the L formation elements when the whole is assembled. Gaps may be provided at the ends of the elements as desired or in the middle.

A modified form uses 5. formation elements, the central T formation element being replaced by two L formation elements arranged back to back and forming a built-up '1 formation element. Hereinafter, whenever i formation element is referred to, it is intended that two L formation elements back to back will be the equivalent thereof, umess from the context or by direct statement this is not intended.

Referring now to the figures, attention is first invited to Fi 2 so that the purpose of the various parts of the invention will be known and appreciated. There is illustrated therein an example of a complete circuit for igniting and operating two gaseous discharge devices, which are symbolically represented here as fluorescent hot lamp L ignites, and then the lamp L cathode lighting lamps L and L connected in series and across a primary winding P and a secondary winding S. A reactive element in the form 'of a condenser C is also in the series circuit, and a starting condenser C is shunted across the lamp L It being intended to illustrate a series sequence starting, series operating, ra id start circuit, there are continuously activated filaments at the ends of the lamps and these are provided with their current by means of filament windings F F and F closely coupled to the primary winding P or tapped therefrom. The transformer core is designated as 12 in said FIG. 1.

The operation of the circuit is well-known; First the The primary and secondary windings are in auto-transformer relation across the line .and their combined voltage eventually supplies the two lamps operating in series, with the leaky nature of the transformer 12 providing leakage reactance for operational ballast after ignition.

In FIG. 1 there is illustrated a transformer 12 which may have the circuit of FIG. 2 associated therewith. Thertransformer 12 is formed of three elements, a pair of outer L formation elements 14 and a single inner T formation element 16. The L formation elements 14 have a long leg 15 and a short leg 17 and the T formation element has a single elongate leg 19 and a cross arm 21. The transformer 12 is constructed by assembling two L formation elements 14 with their short legs 17 facing inwardly and sandwiching a T formation element 16 therebetween with the cross arm 21 at the opposite end relative the short legs 17. The dimensions of the elements are chosen such that the length of the cross arm 21 is exactly the distance between the inside of the long legs 15 of the L formation elements, thereby providing for parallel arrangement of all long legs. There are also formed elongate spaces between the central elongate leg 19 and the outer long legs 15. These spaces form the winding window, and windings wound upon the central elongate leg 19 will fit therein. For example in the left hand end of the window there is provided winding P and the filament windings F F and F while on the right hand end there is the winding S. The space 22 between windings may be left empty or provided with a shunt. Likewise the junctures 23 may have gaps, or a gap may be provided on the interior of the winding S at 24 for limiting saturation in the vicinity of said winding, if the circuit is leading.

To secure the transformer 12 in assembled relation various means may be used. There we shown two such means. Rivets 25 may be used in conjunction with bridging bars, one such being illustrated atr27. Likewise, the ends of the outer edges of the L formation elements 14 may be notched as at 2? (FIG. 1a) to receive thereon spring-fingered clamps, such as at 31 in FIG. lb, the end fingers 3t fitting the notches, and the side fingers 39 seizing the face of the stacked laminations.

In FIG. 3 there is illustrated an arrangement 'ofrelements 14 and 16. It will be noted that there is a pair of back to back L formation elements between each T formation element, and that presuming a continuous strip of steel of width 33 the only scrap which results from the arrangement consists of the rectangles The broken lines of the figure represent places where the notches 29 may be formed by punching. The direction of movement of the strip of metal would preferably be perpendicular to the elongate legs of the elements.

In case it is not convenient to provide for automatic separation of elements at the punching machine, or for other reasons, it may be desirable to form the T formation elements 16 and the L formation elements 14 separately. In FIG. 4 T formation elements are being formed, and it will be seen that they are nested with the cross arms alternately to the right and left. In FIG. 3 all cross arms 21 were arranged along one side while all of the short legs of the L formation elements were arranged on the opposite side. The only scrap resulting from the arrangement of FIG. 4 is represented by the very small rectangles 35. In FIG. 5 only L formation elements are being formed. The short legs are on alternate sides and face in the same direction, along the length of the strip (not shown). There is very little scrap in this method, only the narrow slit 37 being discarded. The broken lines here also represent notches 29 if desired.

FIG. 6 is an illustration of a varied form of arrange ment for producing only L formation elements with very little scrap. Note the small rectangle 35 which occurs only once for every two elements.

FIG. 7 illustrates a form of the core of the transformer 12 which is made up only of L formation elements 14. Here the outer or framing side elements 14 are the same as in FIG. 1, but the inside or winding leg element 16 has been replaced by two back to back L formation elements. The windings are not here illustrated.

It is desired to point out that the shell core of the transformer 12 has a central winding leg, which is formed of the elongate leg 19 in FIG. 1 and two long legs 15 in FIG. 7. It has elongate framing side legs which are formed of the long legs 15 of the outer elements 14 in both FIGS. 1 and 7. It has end bridging members which are formed in FIG. 1 as follows 7 On the left end by the cross arm 21 and the ends of the long legs 15;

On the right end by the end of the elongate leg 19 and the short legs 17 of the outer L formation element.

In FIG. 7 the end bridging members are formed as follows:

On the left by the short legs 17 of the two inside back to back L formation elements and the ends of the long legs of the outer L formation elements; on the right by the same parts but of opposite elements.

It is desired to point out that the invention is ideally suited for extremely economical construction and the proportions illustrated should not be considered limiting. For example, the width of the window W can be adjusted within wide limits up to one half the width of the long leg 19. There is no limitation on length of the core or the number of windows and windings for which the same may be designed.

What it is desired to claim is:

1. A method for producing a shell-type transformer core which is comprised of individual laminations of electrical steel stacked and secured together in. a unitary core structure, and in which the laminations consist only of an elongate T-shaped member and an elongate L-shaped member, said T-shaped members are stacked to form the central winding bar of the core and the L-shaped members are stacked and arranged to cooperate with the stack of T-shaped members to form the side parts and bridging end parts of the core; said method comprising, stamping said Tshaped and L-shaped laminations in a continuous process from a sheet of electrical steel passed through a stamping machine, albeit in a predetermined geometric arrangement of said individual laminations along the direction of movement of said sheet whereby said stamping results in substantial reduction in waste, said arrangement providing for pairs of L-shaped members arranged alternately with T-shaped members and with the short leg of each L-shaped member of a pair projecting in opposite directions whereby they may'comprise a T- shaped lamination and with each T-shaped member adapted to be severed along the longitudinal axis of its long leg to form a pair of L-shaped members, each T- shaped member having the cross-head thereof substantially flush with one side edge of the sheet and each L- shaped member having the shorter leg thereof substantially flush with the opposite side edge of the strip, the longer legs of the T and L-shaped members arranged perpendicular to the direction of movement of the sheet through the machine, said arrangement providing for re- 5 duced dimension waste segments of said sheet during said stamping only between ends of adjacent pairs of L-shaped members and only between ends of adjacent T-shaped members.

2. The method as described in claim 1 in which the L-shaped members of each pair are arranged back to back along their longer legs.

3. The method as described in claim 1 in which the combined length of the shorter legs of the L-shaped members of each pair is substantially equal to the length of the cross-head of a T-shaped member.

4. A method for forming respective T and L shaped core laminations for use in a fluorescent lamp igniting transformer wherein the long leg of a T forms a central Winding leg and L laminations together with the cross-head of the T form, a peripheral winding leg in each of a plurality of lamination layers of the transformer, the improvement comprising the step of forming T-shaped laminations from a strip with the cross-head of each successive T at opposite sides of said strip and the step of severing certain of said T-shaped laminations along the longitudinal axis of the long leg to form a pair of L-shaped laminations with opposingly projecting short legs.

5. A method for producing a shell-type transformer core which is comprised of individual laminations of electrical steel stacked and secured together in a unitary core structure, and in which the laminations consist only of elongate T-shaped members and elongate L-shaped members, and said T-shaped members are stacked to form the central winding bar of the core and the L- shaped members are stacked and arranged to cooperate with the stack of T-shaped members to form the side t5 parts of the core, said method comprising, stamping said T-shaped and L-shaped laminations in a continuous process from a sheet of electrical steel passed through a stamping machine, albeit in a predetermined geometrical arrangement of laminations in groups thereof along the direction of movement of said sheet whereby said stamping results in substantial reduction in waste, the said arrangement of groups each providing for a pair of L- shaped members arranged alternatively with a T-shaped member and with the short leg of each L-shaped member projecting each toward one another, the inner edges of the long leg of the L-shaped members of each said group being common with and defining the long leg of the T-shaped member of said group, the T-shaped member having the crosshead thereof abutting the ends of the long legs of the L-shaped members which are opposite to those ends having the respective short legs.

6. The method as defined in claim 5 in which the stamping is accomplished as the strip is passed through the stamping machine with the long legs of the T and L- shaped members perpendicular to the direction of movement of the said strip.

7. The method as claimed in claim 5 in which the long legs of the T and L-shaped members are stamped side by side.

References (Cited in the file of this patent UNITED STATES PATENTS 354,170 Myers Dec. 14, 1886 1,536,027 Mortimer Apr. 28, 1925 FOREIGN PATENTS 277,164 Germany July 30, 1914 Patent No. 3, 153 961 October 27 1964 Albert E. Feinberg et alt ears in the above numbered patthat error app s Patent should read as It is hereby certified ent requiring correction and that the said Letter corrected below.

line l6 strike out "cross-head of the T form Column 5, a peripheral winding leg in" and insert instead cross-head of the T form a pheripheral framing leg in Signed and sealed this 2nd day of March 1965;

EDWARD J. BRENNER Commissioner of Patents 

1. A METHOD FOR PRODUCING A SHELL-TYPE TRANSFORMER CORE WHICH IS COMPRISED OF INDIVIDUAL LAMINATIONS OF ELECTRICAL STEEL STACKED AND SECURED TOGETHER IN A UNITARY CORE STRUCTURE, AND IN WHICH THE LAMINATIONS CONSIST ONLY OF AN ELONGATE T-SHAPED MEMBER AND AN ELONGATE L-SHAPED MEMBER, SAID T-SHAPED MEMBERS ARE STACKED TO FORM THE CENTRAL WINDING BAR OF THE CORE AND THE L-SHAPED MEMBERS ARE STACKED AND ARRANGED TO COOPERATE WITH THE STACK OF T-SHAPED MEMBERS TO FORM THE SIDE PARTS AND BRIDGING END PARTS OF THE CORE; SAID METHOD COMPRISING, STAMPING SAID T-SHAPED AND L-SHAPED LAMINATIONS IN A CONTINUOUS PROCESS FROM A SHEET OF ELECTRICAL STEEL PASSED THROUGH A STAMPING MACHINE, ALBEIT IN A PREDETERMINED GEOMETRIC ARRANGEMENT OF SAID INDIVIDUAL LAMINATIONS ALONG THE DIRECTION OF MOVEMENT OF SAID SHEET WHEREBY SAID STAMPING RESULTS IN SUBSTANTIAL REDUCTION IN WASTE, SAID ARRANGEMENT PROVIDING FOR PAIRS OF L-SHAPED MEMBERS ARRANGED ALTERNATELY WITH T-SHAPED MEMBERS AND WITH THE SHORT LEG OF EACH L-SHAPED MEMBER OF A PAIR PROJECTING IN OPPOSITE DIRECTIONS WHEREBY THEY MAY COMPRISE A TSHAPED LAMINATION AND WITH EACH T-SHAPED MEMBER ADAPTED TO BE SEVERED ALONG THE LONGITUDINAL AXIS OF ITS LONG LEG TO FORM A PAIR OF L-SHAPED MEMBERS, EACH TSHAPED MEMBER HAVING THE CROSS-HEAD THEREOF SUBSTANTIALLY FLUSH WITH ONE SIDE EDGE OF THE SHEET AND EACH LSHAPED MEMBER HAVING THE SHORTER LEG THEREOF SUBSTANTIALLY FLUSH WITH THE OPPOSITE SIDE EDGE OF THE STRIP, THE LONGER LEGS OF THE T AND L-SHAPED MEMBERS ARRANGED PERPENDICULAR TO THE DIRECTION OF MOVEMENT OF THE SHEET THROUGH THE MACHINE, SAID ARRANGEMENT PROVIDING FOR REDUCED DIMENSION WASTE SEGMENTS OF SAID SHEET DURING SAID STAMPING ONLY BETWEEN ENDS OF ADJACENT PAIRS OF L-SHAPED MEMBERS AND ONLY BETWEEN ENDS OF ADJACENT T-SHAPED MEMBERS. 